I. Field of the Invention
The invention relates generally to syringes and similar devices for injection of fluids into an organism or other entity and particularly relates to a degradable or self-destructing syringe capable of only a single use.
II. Description of the Prior Art
Transmission of diseases such as acquired immune deficiency syndrome (AIDS), hepatitus, etc. often occurs due to the sharing of syringes by intravenous drug users. In order to prevent the spread of various diseases by this transmission route, it has long been known in the art to provide syringes and similar devices which become inoperative after only a single use. Most such devices are mechanical in nature with the syringe needle or other portion of the syringe being destroyed either by virtue of the normal injection motion when the syringe is used or by some deliberate action by a user. Syringes which "destruct" without any deliberate action on the part of a user would, of course, be more effective in preventing disease transmission by intravenous drug users since such persons usually wish to maintain a syringe in useable condition so that the syringe may be shared. Again, certain syringes have previously been developed which become inoperative after a single use although most such devices are impractical due to complexity and expense. The art has, however, advanced to a state whereby certain syringes are known which become inoperative after only one or after only a few uses and which are not mechanically complex and which require little structural variation from the structure of a typical syringe. In U.S. Pat. No. 4,781,683 to Wozniak et al, a single-use, self-annuling injection syringe is disclosed which includes a hydrophilic expansion plug positioned in the outlet flow channel of the syringe. The expansion plug expands after being exposed to a material containing water and thereby renders the syringe inoperative by blocking the outlet flow channel of the syringe. As a further example, Johnson provides in U.S. Pat. No. 4,816,021, a self-destructing hypodermic device intended for only a single use. In Johnson, at least some portion of the syringe, such as the casing, plunger or the like is comprised of a material which is at least partially soluble in the medications or solutions intravenously injected through use of the device. Accordingly, those portions of the Johnson syringe destruct after only one or a few uses and therefore do not allow continued use of the syringe.
The need continues to exist in the art for a single-use syringe which readily and rapidly degrades and becomes inoperative after a single use without the requirement for any deliberate action on the part of a user of the syringe. The need further exists for a syringe which is not mechanically complex or expensive and which has a structure which varies as little as possible from the structure of a typical syringe. A need further exists in the art for a pre-filled syringe which will become unuseable after only a single use. The present invention addresses these needs in the art by providing a syringe having a structure which is similar to the structures of typical syringes and which is therefore readily fabricated but which also becomes inoperative after only a single use or only a few uses without requiring a deliberate action on the part of a user. In order to accomplish these objectives, the syringe of the present invention mounts a needle to a main body of a syringe by means of structural portions which are formed of a material which is at least partially soluble in or absorbant by the medication or solution used with the syringe, thereby preventing the needle from being retained in an operative position on the syringe after a first use of the syringe.